Today, I got into the exhaust spigot replacement for the left jug. The spigot that was in that port was pretty long in the tooth and the fit was sloppy.

Bought a standard replacement from a Steve at M&S and fit it to the head. It did not bottom out in the port, which is required to assure it will not come loose and destroy the threads with vibration and time. Since the threads in the port do not go all the way to the bottom, it is customary for the spigot to have the first two theads removed. I'm not expert here. Just did my research here before starting this job.

I measured the depth from the outside edge of the port to the bottom of the square base inside the port. It measured 0.885 deep. Threaded portion of the spigot was less than that. So that means I had to not only relieve the two threads at the start of the thread, but also machine relieve at the end of the thread so it could screw further into the head.

It took a few iterations because I wanted to sneak up on it and remove as little material from the spigot as possible. Here are the pics moving thru the process.

Here's the port. Note that I used a black magic marker to blacken the bottom shoulder of the threaded section of the port.

Here is the new spigot before any mods. Note that the total thread length is less than the total depth of the port, which is shown on the indicator dial.

Here is a view of the first threads of the port. Note that they are a little beat up. This means my new spigot could probably screw in deeper than it would if the threads were pristine. But this is still not enough relief to let it bottom in the port.

Here is the spigot in my lathe with my first relief cut on the first threads. Normal practice is for the spigot to be made with the first two threads removed by machining down to the minor diameter of the thread. Mine did not have this relief. The pitch is 16 TPI which is a nominal 0.048 inch/thread. So, two threads would be 0.096 inch. I machined 0.090 off in this picture and tried it in the head to see what the effect would be. It now screwed all the way in until the end of the threaded portion was out of sight. But still no contact on the bottom shoulder face.

Back in the lathe for the second relief cut. This is at the end of the threads. I machined material away until I had 0.010 inch more length than the depth of the port. That made it 0.895 inch. Here is the spigot with both relief cuts finished.

Also missing from the spigot was the gradual taper at the exhaust pipe end that lets the gas expand into the header. The smaller the step from the spigot to the header ID, the less turbulence is created by the exhaust gasses. I cut a 10 deg taper in this area.

I ended up having to put the spigot in the lathe again and machine a bit more off the front threads. The spigot was still bottoming on the bottom threads in the port and not the shoulder face. I machined the relief to 0.110, which is another 0.014 inch. With that done, I screwed the spigot in, tightened it and then removed it to check for contact. I had a nice silver line in my black magic marker all around the face of the shoulder in the port. The dental instrument is pointing to the contact line in this pic.

So, with this accomplished, the spigot is now held tightly against the face of the port. This does two things. First, it gives it a flat surface against which it is compressed, thus preventing it from tipping side to side from vibration or the exhaust pipe moving. Second, it loads all the threads on one flank, all the way around. this provides both the compressive force holding it against the bottom of the port as well as puts opposing lateral forces all around the spigot keeping it from moving side to side. It should not come loose.

As a sidenote, I took a much closer look at the right spigot and it appears to be cross threaded in the head. The spigot is bottomed out on one side and not touching on the other. However, it is rock solid in the head. I tried to remove it and cannot. I suspect the combination of cross threading and carbon have locked it in place. So, I'm going to leave it and just keep an eye on it. If I remove it now, I'll probably have to retap the head and make a custom spigot. I'll have to do that if it comes loose over time so I have nothing to lose if I monitor it rather than change it now. If it comes loose, I know how to fix it. But it won't be fun. If it stays tight, I won for a change.

Over the last few days I've been fitting the front end to the bike. Part of the process was making sure everything looked right before I started torquing bolts. If you have been following this thread, you know that there was a false start on the front end a month or so ago. I've since determined that the gaiters I have are correct for my year and will use them along with the correct band clamps.

I made new cork washers that go between the top spring abutment on the forks and the bottom of the lower yoke. When I installed the forks into the yokes, the washers did not look right at first so I posted an inquiry in the general forum. Several folks on this site and the Britbike site confirmed they were correctly positioned. Just had to skooch up the gaiters a bit.

My homemade fork installation tool worked perfectly. It was shown earlier in the thread during the first fork installation attempt.

During the fit-up checks I noticed that there is some clearance between the fork covers (headlight ears) and the bottom of the top yoke. I do not remember seeing this when the bike came apart. I suspect it might be due to the tapered roller bearing I installed in place of the old ball bearings in the steering head. So, to take up the gap, I put a 0.125 cross section o-ring that fit snug on the fork tube.

I used the old fork caps to draw the forks into the top yoke (80 ft-lbs of torque required) and then removed them and installed the new caps. I put o-rings on those caps to help seal the tubes from oil seepage.

I then fit the two teardrop shaped front fender brackets with the slotted hole to the lugs on the fork sliders. Powdercoating on both parts made the fit too small so I had to file off some of the paint and then tapped them in place with a dead blow mallet. Took them off, cleaned up any paint that was shaved off and then tapped them back onto the lugs.

Next was the front wheel. I lifted the front of the bike up by putting a 2x4 under the front section. This gave me enough clearance to get the wheel under the forks. Four bolts later and the front end is together short of the front fender.

Here are some pics of the bits mentioned above.

Cork washer that goes between upper spring abutment and bottom of lower yoke. Need to pull up the socks (gaiters) to hide these.

Here is a shot of the o-ring I put at the top of the fork cover to hide the gap. Also adds some rigidity to the cover which can't hurt.

Here's the front end together on the bike. See that striped towel under the front of the frame. It's covering the 2x4 that held the frame at this angle to allow the wheel to be placed under the forks.

Another view of the completed front end. Note that I pulled up the socks and you cannot see the cork washers anymore.

My fender was an original I got off ebay because if you remember, the fenders that came on my bike were painted. The fender came with the correct brackets, but I had already had my brackets powder coated so just left the others on the bench.

Well, my brackets needed a bit of tweaking before the fender sat properly. It is still not perfect, but probably as good if not better than how the left Meriden based on what I've been told and read.

Instead of fiber washer under the fender to isolate it a bit from vibes, I was going to make or buy rubber washers. That's what I found when I took it apart. But when I was at Fastenal picking up some fasteners and stocking up on stainless washers, I found a bin that said "stainless bonded rubber sealing washers". They are a stainless washer with a rubber washer bonded to it. Needless to say, I bought 4 for the fender to try them out and they worked great. Made things a bit easier.

Shocks went on with only one hitch. I bought UNF stainless 18-8 bolts and polished the heads for the shock mounts. I also bought stainless nuts, although I'm not a big fan of stainess fasteners due to the tendency to gall. Although, I have to admit, I have not had a stainless nut and bolt gall in many years. Well, I can't say that anymore. Bottom bolt and nut on first shock galled. Just barely got them apart. So, that was all I needed. Tossed the stainless nuts in the stainless fastener box and put zinc plated carbon steel nuts on the stainless bolts with blue Locite.

I love the lines of the blade fenders. I am a firm believer that the fender should follow the contour of the tire. It's such a clean look.

Also missing from the spigot was the gradual taper at the exhaust pipe end that lets the gas expand into the header. The smaller the step from the spigot to the header ID, the less turbulence is created by the exhaust gasses. I cut a 10 deg taper in this area.

It might surprise you that I don't try in any way to blend the spigot outlet to the pipe diameter,because it would encourage exhaust reversion.
When I make a spigot,it usually gets bored through at around 1-1/32"to 1-1/16" diameter and only blended at the valve end with a 30 degree included angle.The standard exhaust port size is overly generous.

It might surprise you that I don't try in any way to blend the spigot outlet to the pipe diameter,because it would encourage exhaust reversion.
When I make a spigot,it usually gets bored through at around 1-1/32"to 1-1/16" diameter and only blended at the valve end with a 30 degree included angle.The standard exhaust port size is overly generous.

Yes, that does surprise me but, I am at best a reasonable layman when it comes to engine tuning and have never heard of exhaust reversion. The stock spigots on my 70 have the blend much like Rob machined on his. Did the engineers of the day use assumptions regarding this feature? I Googled the topic and found some supporting information about using a step from an exhaust port to the exhaust pipe to reduce exhaust reversion. Very interesting stuff.

Mr. Pete. That is interesting. I am familiar with exhaust reversion. To be honest, I simply modified the exhaust end of the new spigot to match the spigot that is firmly seated in the head. Too late now. If that cross threaded spigot comes loose with time, I guess I replace them both and eliminate that taper. There is still a step at the mouth so not fully blended into the header.

After much study, frustration, false starts, a trip to Hutch's shop for an exchange fender, a discussion with John Healy on the phone regarding repop stainless rear fenders and a discussion with a very talented vintage car restoration shop owner, I manage to fit the new rear fender to the bike.

According to John Healy, who imports these fenders, they are all a little warped, twisted, improperly formed, call it what you will, so the are not a drop in fit. Since I probably have a good 20 hours or more into monkeying with this fender, not including the 6 hour round trip to Hutch's shop, I thought I'd provide my opinion on how you should proceed to install these fenders, if you are lucky enough to find one.

Before I begin, John said the maker in the UK, Chris something, is not making them anymore. Don Hutchinson has two left in his shop. Not sure how many others are available. Hutch has his listed on ebay.

Since the fender is not properly formed, you will need to use the mounting points on the bike frame to hold the fender correctly positioned so that you can pull, pry or otherwise reshape the fender to fit the frame.

I suggest you start with the front mounting hole. I suggest starting with this hole since the position of this part of the fender is critical as it must provide clearance for the chainguard and the oil tank.

My old fender had about 1/2" clearance from the swingarm so that point was established with a small piece of wood taped to the swingarm. With the fender positioned correctly relative to the swingarm mount and using my old fender to establish reference points on the frame, I marked the forward mounting hole and drilled it. Then with a bolt thru that hole into the forward bracket, position the fender to establish the relative position of the fender to the frame. With the rear of the fender centered to the frame, mark the holes for the top strap that mounts between the shocks. Remove the bolt at the front mount and let the front of the fender go where it wants. Using the reference marks for the top strap hole, center the fender in the frame so it is straight relative to vertical and remark the holes for the top strap. The two sets of holes marked will probably be close, but not the same. I did this exercise several times to make sure I had the fender properly aligned. I then took a carpenter's square and using the side of the fender, marked a line thru the marked holes that was perpendicular to the side of the rear half of the fender. I then refit the fender to see how those marks aligned. When I was happy they were properply located to make the rear of the fender properly positioned, I drilled them.

Next was the strap that goes over the rear frame tube. Same exercise, mark and drill. Last is the two rear bracket/lift handle bolts. Repeat the alignment exercise then mark and drill the holes.

With all the holes drilled, using rubber washers to protect painted surfaces bolt the fender to the frame. Start with the top strap between the shocks, then the rear strap over the frame and finally the rear bracket/lift handle. With those all tight and the rear of the fender straight and centers, work the front section with your hands, a piece of wood and a frame tube as a fulcrum or any other means that will not damage the fender and bend the front portion where it needs to be. It will take some force since the stainless likes to spring back. Use towels to protect your frame paint and with some effort and patience, it will move to where it needs to be.

Here are the various brackets that need to be fit in the order they were fit.

Front bracket. This the first hole you need to drill.

This shows the relationship of the front fender to the chainguard bracket on the swingarm. Bracket is casting a shadow on the masking tape that shows the fender clears the bracket.

Here's the piece of wood that established the proper spacing from the swingarm.

Here is the second bracket you need to fit and drill the holes in the fender.

This is the next bracket you need to fit.

Here is the last bracket to be fit and for which you need to drill holes.

I used a string attached to the top yoke to establish a straight line down thru the frame and to check the position of the fender as it was fit to the bike.

Here is the fender after final fit to the frame. Bolting is temporary.

Mounted fender from the other side.

Remember the rubber washers as they will slightly impact alignment and hole positioning.

Tomorrow I'll mount the taillight. Then I'll inventory the fasteners I'll need and head to Fastenal for new stainless fasteners, fender washers, locknuts, etc.

Register Now

In order to be able to post messages on the Triumph Forum: Triumph Rat Motorcycle Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:

If you do not want to register, fill this field only and the name will be used as user name for your post.

Password

Please enter a password for your user account. Note that passwords are case-sensitive.

Password:

Confirm Password:

Email Address

Please enter your valid email address, that can receive an automated confirmation message. Otherwise, you won't be able to gain full access.

Email Address:

Log-in

User Name

Remember Me?

Password

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.